Foaming of rigid PVC/wood-flour composites through a continuous extrusion process

The effects of chemical foaming agent (CFA) types (endothermic versus exoth ermic) and concentrations as well as the influence of all-acrylic processin g aid on the density and cell morphology of extrusion-foamed neat rigid. PV C and rigid PVC/wood-flour composites were studied. Regardless of the CFA t ype, the density reduction of foamed rigid PVC/wood-flour composites was no t Influenced by the CFA content. The cell size, however, was affected by th e CFA type, independent of CFA content. Exothermic foaming agent produced f oamed samples with smaller average cell sizes compared to those of endother mic counterparts. The experimental results indicate that the addition of an all-acrylic processing aid in the formulation of rigid PVC/wood-flour comp osite foams provides not only the ability to achieve density comparable to that achieved in the neat rigid PVC foams, but also the potential of produc ing rigid PVC/wood-flour composite foams without using any chemical foaming agents.